1. FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a lamination capacitor and, more particularly, connector terminal electrode thereof.
2. DESCRIPTION OF THE RELATED ART
A lamination capacitor in general consists of a hexahedral ceramic main body part, a plurality of internal electrodes which divide the ceramic main body part into a plurality of alternating ceramic layers, and connector terminal electrodes which are formed on each side of the ceramic main body part so that they can make an electrical contact with internal electrodes.
Firm contact between the connector terminal electrodes and the internal electrodes is important for the lamination capacitor to prevent decrease in electric capacity and increase in dielectric loss tangent. Therefor, after calcining a ceramic main body part having the plurality of internal electrodes therein, the calcined ceramic main body part is subjected to a barrel finishing step to expose the internal electrodes from the sides of the ceramic main body part. Thereafter, the connector terminal electrode is formed on each side of the ceramic body part.
These steps will be described more specifically to reference with figures. A lamination capacitor has a calcined ceramic main body part containing internal electrodes 11a, 11b and 11c arranged in alternating layers. In a ceramic main body part 10 of FIG. 1A, the internal electrode 11b is exposed from the side of the ceramic main body part. However, in general there is many cases where internal electrodes are not exposed from each of the sides of the ceramic main body part because the internal electrodes made of palladium (Pd) shrink during calcining process. FIG. 1B shows in section a ceramic main body part in such a state where the internal electrodes 11a,11b and 11c are not exposed very much from each side of it.
Therefor, the ceramic main body part is subjected to a barrel finishing step in order to expose the internal electrodes from the sides of the ceramic main body part. In spite of barrel finishing, the internal electrodes 11b and 11c is not exposed well as shown in FIG. 2. Thereafter, referring to FIG. 3, a connector terminal electrode 20 is formed on each of the sides of the ceramic main body part of FIG. 2 by using technique of prior art.
Specifically, silver (Ag) powder or a mixture of a silver powder and a palladium powder, glass frit and bonding material is mixed into a paste. This paste is applied onto the sides of the ceramic main body part 10 and is calcined at a temperature of 750.degree. C. through 850.degree. C. Thereafter, nickel is plated on the calcined paste to finish the terminal electrode 20. Note that soft solder or tin may be plated thereon.
However, though as shown in FIG. 3 the internal electrodes 11a and 11c connect with the terminal electrode 20 the internal electrode 11b is disconnected with the terminal electrode 20. Note that the internal electrode 11c is loosely connected with the terminal electrode 20. Such a contact is referred to as "loose contact".
Such a disconnection between the internal electrode and the connector terminal electrode 20 is because the internal electrodes are not exposed well from each of the side of the ceramic main body part 10 when the connector terminal electrode 20 is formed on each of the side of the ceramic main body part 10. The failure of exposure is due to the following cases:
When the barrel finishing is not complete enough to expose the internal electrodes.
When the internal electrodes are too thin.
When the exposed portion of the internal electrodes is damaged.
When the ceramic layers cover with the internal electrodes.
These facts lead to decrease in electric capacity and increase in dielectric loss tangent in a lamination capacitor. In particular, temperature compensated lamination capacitors suffer from these problems because the temperature compensated capacitor has a small tolerance of both electric capacity and dielectric loss tangent.